Many applications rely on sensor networks or data acquisition or aggregation networks in order to electronically monitor events in an area. For example, sensor networks are used in tunnel activity detection systems where the networks can provide alerts about intruders, in forest fire detection systems, in battlefield observations, in seismic or acoustic monitoring/detection systems, and in other applications where gathering sensor data may be desired. Sensor networks generally include several sensors or transducers (e.g., geophones, hydrophones, heat sensors, fire detectors, motion sensors, cameras, etc) that are deployed within an environment such that data from the sensors can be received by a processing unit for analysis via a common communication channel. These sensor networks are generally unmanned and may be deployed in hostile environments where they are expected to function properly over an extended period of time without requiring complex infrastructure for maintenance. Sensors that are bulky, costly, or that require complex control or monitoring are not well-suited to such applications because of the escalating costs of maintenance.
Conventional sensor networks have several vulnerabilities. For example, some prior approaches had complex control and inter-channel skew management requirements, usually requiring that each node independently synchronizes its transmissions to individual GPS receivers and emit their data asynchronously over an Ethernet or WiFi network. In networks that employed time-multiplexing of separate data packets from each sensor node, the nodes required carefully-timed techniques that involve sequentially querying each node for its data from the data receiver to reduce collision-mediating network bandwidth requirements. In these networks, special-purpose nodes typically must be interspersed amongst data-acquisition sensor nodes to ensure proper function. This complexity adds to the cost of deployment, maintenance, and often compromises the resilience of the network.
Accordingly, sensor networks that have improved fault resilience without requiring complex monitoring or fault diagnosis are desirable. It is particularly desirable that such networks employ relatively low-cost sensor nodes and that the overall network be modular, extensible, and have low maintenance costs.